When water residual on a bowl surface is evaporated after washing the bowl surface of a closet bowl or a urinal by washing water and the bowl surface is evaporated, water scale may be attached to the bowl surface. If the water scale is attached to the bowl surface, the bowl surface is smeared. Further, since the water scale is robustly attached to the bowl surface, the water scale cannot be removed without difficulties. Therefore, there is a demand for a technique of inhibiting formation of the water scale, or a technique which can easily remove the water scale even in the case that the water scale is attached to the bowl surface. Further, the water scale of silicic acid component is adhered to a glaze surface of a toilet bowl more robustly than the water scale such as calcium component and magnesium component. Accordingly, there is strongly desired a technique which can easily remove the water scale of the silicic acid component.
There has been proposed a sanitary washing device which previously removes calcium ions and magnesium ions which form the water scale component (JP-A-2004-270185). However, the sanitary washing device described in JP-A-2004-270185 has a problem that the device becomes large in size.
Further, there has been proposed a sterilized raw tap water supply type washing household equipment which forms sterilized raw tap water having hydrogen ion concentration between pH 4 and pH 6, and supplies the sterilized raw tap water to a subject to be washed (JP-A-H07 (1995)-136660A). Further, there has been proposed a water washing type closet bowl which delivers function water to the bowl portion after a predetermined time has passed after a washing operation (JP-A-2004-92278). However, JP-A-H07 (1995)-136660 and JP-A-2004-92278 do not have any description about the water scale of the silicic acid component, and there is room for improvement in a point of inhibition of the formation of the water scale or a point of easy removal of the water scale.